CASL: The Consortium for Advanced Simulation of Light Water Reactors A DOE Energy Innovation Hub for Modeling and Si

1. CASL: The Consortium for AdvancedSimulation of Light Water ReactorsA DOE Energy Innovation Hub for Modeling and Simulation of Nuclear Reactors Jess Gehin Focus Area Lead Advanced Modeling Applications CASL Reactor Technology R&D Integration Lead Oak Ridge National Laboratory North American Workshop on Beta-delayed Neutron Emission JIHIR, ORNL May 2, 2013

2. CASLA DOE Energy Innovation Hub in the Office of Nuclear Energy Mission Provide leading edge modeling and simulation capabilities to improve the performance of currently operating Light Water Reactors Vision Predict, with confidence, the performance and assured safety of nuclear reactors, through comprehensive, science-based modeling and simulation technology that is deployed and applied broadly within the U.S. nuclear energy industry Goals • Develop and Effectively Apply Modern Virtual Reactor Technology • Provide More Understanding of Safety Margins While Addressing Operational and Design Challenges • Engage the Nuclear Energy Community Through Modeling and Simulation • Deploy New Partnership and Collaboration Paradigms` • First Introduced by Secretary Chu in the President’s FY2010 Budget • A Different Approach • “Multi-disciplinary, highly collaborative teams ideally working under one roof to solve priority technology challenges”– Steven Chu • “Create a research atmosphere with a fierce sense of urgency to deliver solutions.”– Kristina Johnson • Characteristics • Leadership – Outstanding, independent, scientific leadership • Management – “Light” federal touch • Focus – Deliver technologies that can change the U.S. “energy game”

3. CASL Scope: Develop and apply a “Virtual Reactor” to assess fuel design, operation, and safety criteria • Deliver improved predictive simulation ofPWR core, internals, and vessel • Couple Virtual Reactor to evolving out-of-vessel simulation capability • Maintain applicability to other NPP types • Execute work in six technical focus areas to: • Equip the Virtual Reactor with necessary physical models and multiphysics integrators • Build the Virtual Reactor with a comprehensive, usable, and extensible software system • Validate and assess the Virtual Reactor models with self-consistent quantified uncertainties Focus on Addressing Challenge Problems to Drive Development and Demonstration

4. CASL Challenge ProblemsKey safety-relevant reactor phenomena that limit performance CASL is committed to delivering simulation capabilities for Advancing the understanding of key reactor phenomena Improving performance in today’s commercial power reactors Evaluating new fuel designs to further enhance safety margin

5. CASL: Challenge Problem (CP) Objectives • CRUD (CRUD Induced Power Shift / CRUD Induced Localized Corrosion) • Inform PWR core CRUD risk assessment for margin management decisions; reduce uncertainty in CRUD thickness & boron uptake predictions • GTRF / FAD (Grid-To-Rod Fretting / Fuel Assembly Distortion) • Inform fuel assembly structural features, materials, and geometry relationship to fuel system performance; identify core locations and geometric characteristics contributing to flow conditions impacting fuel structural stability • PCI (Fuel Pellet Clad Interaction) • Predict cladding stress and strain, inform margins imposed, and inform fuel pellet-clad geometry relationship to performance during a power maneuver • DNB (Departure from Nucleate Boiling) • Identify sources of conservatism and margin in current practices for typical reload DNB evaluations and on specific DNB correlation calibration experiments • Cladding Integrity during a LOCA • Assess fuel performance s during a LOCA and identify sources of conservatism and margin • Cladding Integrity during a RIA • Assess fuel performance during a RIA transient and identify sources of conservatism and margin Significant Progress on CRUD, GTRF, PCI CPs Increasing effort on DNB, Cladding Integrity CPs

6. CASL Organization Stable yet evolving as required

7. CASL Tackles the Multi-Scale Challengeof Predictively Simulating a Reactor Core From full core to fuel assembly to fuel subassembly to fuel pin/pellet

8. Virtual Environment for Reactor Applications (VERA)CASL’s virtual reactor for in-vessel LWR phenomena Advanced Thermal-Hydraulics Research CFD Neutronics Baseline Mechanics Neutron Transport Commercial CFD Chemistry Fuel performance Chemistry Isotopics Corrosion Subchannel Thermal-Hydraulics Nodal diffusion Structural mechanics CRUD Deposition Cross Sections Subchannel Thermal-Hydraulics Geometry / Mesh / Solution Transfer Physics Coupling Infrastructure Reactor System Input / Output

9. Enabling R&D Objectives • Materials Performance and Optimization (MPO) • Mature 3D fuel performance capability with full assessment against CRUD/PCI/GTRF problems. Validated fuel performance models inform assessments of safety margin (PCI) and best operational practices (CRUD, GTRF). Functional capability and partial assessment for RIA- and LOCA-based transient problems. • Radiation Transport Methods (RTM) • Robust 3D pin-resolved transport and prototype hybrid Monte Carlo transport with modern cross section/shielding treatments and coupling to T-H, fuel, and corrosion chemistry capabilities • Thermal Hydraulics Methods (THM) • Robust 3D steady-state/transient turbulent multi-phase capability with subcooled boiling models, an initial assessment of DNB, and complementary with a modern subchannel capability • Validation and Uncertainty Quantification (VUQ) • Mathematical tools and methodologies integrated andaccessible to enable quantifying sensitivities anduncertainties in full-scale multi physics PWR simulations 9

10. CASL Results to Date • Developed and released Virtual Environment for Reactor Applications (VERA) to CASL core partners through ORNL’s Radiation Safety Information Computational Center • Established baseline industry capability and advanced R&D capability in VERA for neutronics, thermal hydraulics, and corrosion chemistry • Applied selected aspects of VERA to operational PWR core scenarios with conditions relevant to corrosion buildup (“crud”), pellet-clad interaction, and grid-to-rod fretting • Integrated within VERA a state-of-the-art sensitivity and optimization capability to support uncertainty analysis of reactor operational and safety scenarios • Demonstrated that newly established multidimensional simulation capabilities exceed industry capabilities in physics modeling

11. Defective (MPS) pellet placed midway between four intact pellets Simulation from fresh fuel state with a typical power history, followed by a late-life power ramp 3D Fuel Performance Model:Peregrine Fuel Temperature Missing pellet surface He fill gas (2 MPa) Von Mises Effective Stress Zr-4 clad

12. Coolant Chemistry and CRUD GrowthThermal hydraulics + transport + fuel performance + chemistry + structural mechanics Boron concentration within crud layer (colored contours) grown within MAMBA over 60 days of operation Large azimuthal variation in fluid/cladding temperature computed Spacer with mixing vanes Variations in crud thickness and boron due to T variations on cladding surface Reduced crud and boron due to turbulence behind mixing vanes CFD computed cladding T for pin # 4 80 cm section of fuel rod

13. Turbulent Flow in Grid-to-Rod-FrettingScoping simulations with the Hydra-TH (LANL) code • Helicity isosurfaces • All models capture some levelof detail in the longitudinal vorticalstructures and swirl • With Spalart-Allmaras, eddies appearmore damped, rotation around rod is smeared ILES DES Spalart-Allmaras End-view of fuel rod showingswirl in coherent structures

14. Neutronics Modeling of Operational Reactors • CASL is developing advanced neutronics modeling capabilities that provide far more detail than current industry practice • CASL reference plant for this analysis is Watts Bar Unit 1 • TVA has provided substantial operational data • Westinghouse is providing industry-level analysis results for comparisons • High fidelity neutronics simulations methods are under development within CASL • ORNL developing high-fidelity, high resolution transport using TITAN • University of Michigan developing capability that can be more readily deployable on industry computers • Neutronicsis being coupled with Thermal Hydraulics and Fuel Mechanics codes to provide a full multi-physics reactor simulation

15. Questions?www.casl.gov or info@casl.gov